What is it about?

The vibrational spectra of condensed and gas-phase systems are influenced by the quantum-mechanical behavior of light nuclei. Full-dimensional simulations of approximate quantum dynamics are possible thanks to the imaginary time path-integral (PI) formulation of quantum statistical mechanics, albeit at a high computational cost which increases sharply with decreasing temperature. By leveraging advances in machine-learned coarse-graining, we develop a PI method with the reduced computational cost of a classical simulation. We also propose a simple temperature elevation scheme to significantly attenuate the artifacts of standard PI approaches as well as eliminate the unfavorable temperature scaling of the computational cost. We illustrate the approach, by calculating vibrational spectra using standard models of water molecules and bulk water, demonstrating significant computational savings and dramatically improved accuracy compared to more expensive reference approaches. Our simple, efficient, and accurate method has prospects for routine calculations of vibrational spectra for a wide range of molecular systems - with an explicit treatment of the quantum nature of nuclei.

Featured Image

Why is it important?

Our work provides a simple, computationally efficient, and accurate approach to simulating quantum dynamics. The proposed technique improves the computational cost scaling of modeling quantum dynamics from O(1/T), a diverging computational cost at cryogenic temperatures, to a constant. Furthermore, it dramatically improves the accuracy of "classical" modeling quantum dynamics.


Conceptually, our approach provides a new perspective towards improving classical methods for modeling quantum dynamics, paving the way towards the rigorous but efficient treatment of quantum dynamics of more complex systems. From a more practical perspective, our technique can enable interpretation and experiments of the plethora of IR/Raman spectra molecular and condensed phase systems at low temperatures, given the dramatic leaps in accuracy and efficiency.

Venkat Kapil
University of Cambridge

Read the Original

This page is a summary of: Quantum dynamics using path integral coarse-graining, The Journal of Chemical Physics, November 2022, American Institute of Physics,
DOI: 10.1063/5.0120386.
You can read the full text:



The following have contributed to this page